A gradual reduction in the dimension of interconnect structures may limit the speed of signal propagation in semiconductor devices. The use of copper and low-k dielectric materials may reduce the delay in signal propagation. However, electromagnetic simulations showed that the diffusion of copper into a dielectric layer will affect the effective dielectric k constant value of the dielectric layer, and that the diffusion effect becomes more significant with increasing diffusion severity that can cause short circuits in integrated circuits. Furthermore, copper is easily oxidized by air, resulting in a relatively short queue time (Q-time) of a chemical mechanical planarization (CMP) process, which is disadvantageous to the development of semiconductor manufacturing processes.